1. Field of the Invention
The invention relates to a process for separating and exhausting gas bubbles from a flowing liquid, especially in a microfluidic system, in which the liquid which contains gas bubbles flows through a deaeration chamber on the way from an inlet point to a discharge point, and to a corresponding device with an inlet point for the entry of a liquid containing gas bubbles and a discharge point for the discharge of the liquid from the device, with a deaeration chamber downstream of the inlet point in the flow direction of the liquid.
2. Description of Related Art
In the process known from microfluidics, the separation of gas bubbles from liquids is achieved in that the water-based liquid which contains gas bubbles flows through a a deaeration chamber which has a wall section of a water-repellent gas separation material which is not permeable to the liquid, but which is permeable to the gas. With this known process, gas bubbles can be continuously (in this sense, therefore, without interruption) removed from a flowing liquid in a microfluidic system. The known process for separating and exhausting gas bubbles from a flowing liquid, therefore, the continuously operating process, requires routing of the liquid to a certain position and in terms of efficiency can still be improved.
Instead of water-based liquids, similar processes can also be carried out for oil-based liquids, possibly also for alcohols or resins. However, in fact, this process has special importance for water-based liquids.
German Patent DE 19 59 679, which forms the starting point of this invention, discloses a filter arrangement, especially for eliminating gas from a liquid flow. The arrangement has a housing with an inlet and an outlet for the liquid. In the housing, between the inlet and the outlet, there is a filter element which can be wetted by the liquid and which is permeable to the liquid, but not to the gas. Upstream of the filter element in the housing, there is a porous element which repels liquid and which is permeable to the gas, but not to the liquid, and which is made essentially flat. Using the porous element, the gas can be separated from the liquid upstream of the filter element and can be discharged through a separate gas outlet. The disadvantage is that the known filter arrangement does not work completely independently of position. Rather, it is necessary for the porous element to be located at least essentially above the liquid in order to be able to achieve gas separation as effective as possible.
European Patent Application EP 1 355 372 A2 and U.S. Patent Application 2003/194369 A1, which were filed before but published after the priority filing date of this application, disclose a chemical reactor which forms an integrated liquid-gas separator and which is surrounded by a water-repellent membrane which is permeable to hydrogen.
U.S. Pat. No. 6,402,821 discloses a position-dependent filter unit for removing impurities and bubbles from a development solution with a bubble filter only on the top.
Published German Patent Application DE 42 19 966 A1 discloses a filter for fluids with a rotationally symmetrical structure with a hydrophilic flat filter and an annular, water-repellent flat filter for self-deaeration, the two filters being located axially one behind the other and flow taking place through them in the same way.
Published U.S. Patent Application 2002/0056675 A1 discloses a position-dependent gas deaeration filter structure with a hollow fiber membrane which hangs loosely into the channel and which is connected to the water-repellent filter.
U.S. Pat. No. 5,989,318 relates to a water separator for separation of a two-phase flow into a liquid water component and a gas component. For purposes of separation, an inner water-repellent filter and an outer hydrophilic filter are used which are made as hollow cylinders and are arranged concentrically, and only gas can be separated radially to the inside by the water-repellent filter. It is not suited for gas separation independent of position.
U.S. Pat. No. 6,267,926 discloses a process and a device for separation of gases from a liquid which is first routed through a filter, and then, in parallel through a water-repellent, microporous membrane tube, gas bubbles being separated from the liquid through the membrane walls by means of negative pressure. This is complex.